There seems to be a difference in behavior depending on which URL you use (although, for the life of me, I can't figure out why--the source code on both is identical). When I access
http://www.saueregger.at/sudoku/ , I can see the background images, the arrows, and the links to the information page and the helper. When I access
http://sudoku.saueregger.at/ , the background image, arrows, and links do NOT display (they are there, but invisible). However, Helmut (Nataraj) and I have been working on it offline. At least I can get it to work, now that I know the arrow buttons are there (the mouse pointer turns from an arrow to a hand).